The major goal of this project is to characterize virus antigens which are the targets of the immune response. This research is focused on measles virus, but is being extended to study HTLV-I. The five proteins of measles virus have been purified and are being used to quantitate antibody in the cerebrospinal fluid (CSF) and blood. Cellular immune responses to each of the five proteins are being assessed by lymphocyte proliferation and cytotoxicity. Most of the research is being conducted with polypeptides from the Edmonston strain of measles virus. The hamster neurotropic strain (HNT) which is neurovirulent and produces chronic CNS infections in experimental animals is also being studied. The biological, immunological, and molecular properties of Edmonston and HNT strains are being compared. Antibody to HTLV-I is being measured in the blood and CSF of patients with tropical spastic paraplegia and patients with other neurological diseases. Efforts to obtain suitable antigenic preparations of HTLV-I for studies of cellular immunity have been initiated.